• Journal of Pharmaceutical Investigation
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• v.20 no.2
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• pp.79-88
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• 1990

A numerical model for diffusion and dissolution controlled transport from dispersed matrix is presented. The rate controlling process for transport is considered to be diffusion of drug through a concentration gradient coupled with time-dependent surface change and/or disappearance of the dispersed drug in response to the dissolution. The transport behavior of drug was explained in terms of ${\nu}$ parameter: ${\nu}$ value means a ratio of diffusion time constant and dissolution time constant. This general model has wide range of application from where release is controlled by the diffusion rate to where release is governed by the dissolution rate. Based on this model, theoretical drug concentration, particle size distributions in the polymer matrix system and the resulting release rate were also investigated.

• Journal of Pharmaceutical Investigation
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• v.19 no.2
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• pp.63-69
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• 1989

Dissolution characteristics of indomethacin (IMC) from hydrophobic polymer solid dispersions were investigated. IMC-polyvinyl chloride (PVC) and IMC-ethylcellulose (EC) solid dispersions were prepared. The dissolution patterns of pure IMC, IMC-PVC and IMC-EC solid dispersions prepared at various ratios (1:1, 1:3, 1:5, 1:9 and 1:19 w/w), and those of corresponding physical mixtures were compared. It was found that the dissolution rates of IMC from solid dispersions with PVC or EC decreased in the order of 1:1>1:3>1:5>1:9>1:19 as the drug to polymer ratios decreased. Also the dissolution rates of IMC from EC solid dispersions increased according to flow rate, but PVC solid dispersions were not affected significantly. After all, PVC and EC matrices could be applied in sustained-release preparation of IMC.

• Polymer(Korea)
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• v.39 no.1
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• pp.33-39
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• 2015

Olmesartan affiliated to biopharmaceutics classification system class 2 is a poorly water soluble drug. For this reason, olmesartan showed a low bioavailability and a lot of difficulties in the process of designing the pharmaceutical formulation. We prepared the solid dispersions of olmesartan. We confirmed the dissolution rate of drug which was prepared by manufacturing. The pharmaceutical formulation of solid dispersions was designed by using PVP as water soluble polymer. We analyzed morphological feature of solid dispersion by employing a scanning electron microscope. Then, the crystalline property of solid dispersion was confirmed through X-ray diffraction and differential scanning calorimeter. Also, the chemical change of solid dispersion was confirmed by the Fourier transform infrared spectroscopy. In vitro dissolution test was used to analyze the dissolution rate of solid dispersion. The prepared solid dissolution olmesartan confirmed the dissolution rate in the pH 1.2. It was compared with olmetec and improved dissolution rate through solid dispersion.

• Journal of Pharmaceutical Investigation
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• v.41 no.6
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• pp.363-369
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• 2011

In this study, we demonstrated the release behavior of carvedilol with the content of polyvinylpyrrolidone K-30 (PVP K-30) and the effect of citric acid and fumaric acid as acidifiers on the release behavior of drug. In addition, it tries to inquire into the release behavior difference of the carvedilol according to the manufacturing method. The release behavior of the tablets was compared with Dilatrand$^{(R)}$ in the simulated gastric fluid (pH1.2). Differential scanning calorimeter (DSC), X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FT-IR) were characterized for the physicochemical properties of the tablets. In case of mixing the carvedilol and PVP K-30, in case the ratio of the carvedilol and PVP K-30 was 1:5, the release behavior was the highest among. As well as the dissolution rate of tablets manufactured by lyophilization and rotary evaporator was higher than physical mixture. The dissolution rate of containing acidifiers was more improved. But, rather the excessive amount of the acidifier addition reduced the dissolution rate.

• Journal of Pharmaceutical Investigation
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• v.6 no.3
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• pp.58-69
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• 1976

It is well established that dissolution is freruently the rate limiting step in the gastrointestinal absorpton of a drug from a solid dosage from. The relationship between the dissolution rate and absorption is particularly distinct when considering drugs of low solubility. Consequently, numerous attempts have been made to modify the dissolution characteristics of poorly water soluble drugs. Since dissolution rate is directly proportional to surface area, one may increase the rate by decreasing the particle size of the drug. Levy has considered a number of methods by which a drug may be presented to the GI fludids in finely divided from. The direct method is the utilization of microcrystalline or micronized particles. A second method involves the administration of solutions from which, upon dilution with gastric fluids, the dissolved drug will precipitate in the form of very fine particles. A more unique way of obtaining microcrystalline dispersions of a drug has been ercently suggested by Sekiguchi et al. They have first proposed the formation of a eutectic mixture of a poorly water soruble drug with a physiologically inert, easily soluble carrier. When such systems are exposed to water or GI fluids, the soluble carrier will dissolve rapidly and the finely dispersed drug particles will then be released. It has been suggested by Shefter and Higuchi that the formation of crystalline solvate could be a powerful tool in affecting rapid disslution of highly insoluble substances. Goldberg et al. have noted that the formation of solid solution could reduce the particle size to a minimum and increase the dissolution rate as well as the solubility of the durgs. It has also been shown that the rates of solution of drugs were appreciably increased by coprectipitating the drug with soluble polymers. The increase was found to be sensitive to the method of preparation, the molecular weight of polymer and the particular ratio of drugs to polymer. Although several investigations have demontrated that the solubility and/or dissolution rates of drugs can be increased in this manner, little information is available in the literature related to the in vivo absorption pattern of drugs orally administered as PVP coprecipitates. Recently, however, it was demonstrated that both the rate and extent of absorption of the insoluble drug could be markedly enhanced when orally administered to rats in the form of a coprecipitate with PVP. The purpose of the present investigation was to ascertain the general appility of soluble polymer coprectation technique as a method for enhancing the in vitro dissolution rate of hydrophobic indomethacin. To accomplish this aim, the dissolution characteristics of pure indomethacin, indomethcin-polymer physical mixtures and indomethacin-polymer coprecipitates were quantitatively studied by comparing their relative dissolution rates. The solubility and dissolution behavior of these systems were also examined.

• Journal of Pharmaceutical Investigation
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• v.38 no.2
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• pp.111-117
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• 2008

To overcome the solubility of poorly water-soluble drug, the formation of solid dispersion using a spray-dryer with polymeric material, that can potentially enhance the dissolution rate extend of drug absorption was considered in this study. $Eudragit^{(R)}$ E100 as carrier for solid dispersion is acrylate copolymer that soluble in acidic buffer solutions (below pH 5.0). It was used to increase dissolution of atorvastatin calcium as a water-insoluble drug in acidic environments. In this study, a spray-dryer was used to prepare solid dispersion of atorvastatin calcium and $Eudragit^{(R)}$ E100 for purpose of improving the solubility of drug. Atorvastatin calcium and $Eudragit^{(R)}$ E100 were dissolved in ethanol and spray-dryed. DSC and XRD were used to analyze the crystallinity of the sample. It was found that atorvastatin calcium is amorphous in the $Eudragit^{(R)}$ E100 solid dispersion. FT-IR was used to analyze the salt formation by interaction between atorvastatin calcium and $Eudragit^{(R)}$ E100. Comparative dissolution study exhibited better dissolution characteristics than the commercial drug ($Lipitor^{(R)}$) as control. The dissolution rate of atorvastatin calcium was markedly increased in solid dispersion system in simulated gastric juice (pH 1.2). This study proposed that this solid dispersion system improved the bioavailability of poorly water-soluble atorvastatin calcium.

• Journal of Pharmaceutical Investigation
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• v.24 no.3
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• pp.139-144
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• 1994

The effect of some formulation variables on the release rate of famotidine, a $H_2$ receptor antagonist, from cellulose matrices containing hydroxypropylcellulose (HPC) in different ratios and types was investigated. The effects of tablet shape and compression pressure on dissolution rate of famotidine were studied. And the effect of the pH of dissolution media was also studied. Increase in the ratio of polymer to drug decreased the release rate of famotidine. Increase of the polymer viscosity also decreased the release rate. The release rate of famotidine was dependent on the pH of dissolution media. The release rate of drug was not much dependent on the compression pressure but dependent on the tablet shape and/or surface area. Consequently, the release rate of famotidine can be modified by changing the HPC contents, types of polymers with different viscosity grades or using appropriate fillers.

• Proceedings of the Korean Fiber Society Conference
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• 2003.10a
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• pp.7-8
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• 2003

Since PVDF/poly(1,4-butylene adipate) blend shows much lower LCST curve compared with PVDF/PMMA blend, the PVDF/PBA blend can be a good candidate for investigating the effect of the electric field on the phase separation and dissolution behavior of an electro-active polymer and electro-inactive polymer blend. (omitted)

• Journal of Pharmaceutical Investigation
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• v.38 no.4
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• pp.249-254
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• 2008

Solid dispersions of poorly water-soluble drug, atorvastatin, were prepared with Eudragit L100 to improve the solubility by spray dryer. To investigate the correlation between physicochemical properties and dissolution rate of solid dispersions, the samples were characterized by scanning electron microscopy (SEM), differential scanning calorimeter (DSC) and fourier transform infrared spectroscopy (FT-IR). SEM and DSC were found that atorvastatin is amorphous in the Eudragit L100 solid dispersion. FT-IR was used to analyze the salt formation by interaction between atorvastatin and Eudragit L100. The dissolution rate of solid dispersed atorvastatin was markedly increased compared to drug powder in stimulated intestinal juice (pH 6.8). Thus, the solid dispersed atorvastatin using the spray drying method with Eudragit L100 may be effective for the bioavailability.

• Journal of Pharmaceutical Investigation
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• v.40 no.5
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• pp.277-283
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• 2010

CoQ with low melting temperature was exploited to improve its solubility by preparing its solid dispersions (SDs) with a meltable polymer, poloxamer 407 (P 407). P407 can be utilized for a relatively simple, quick, inexpensive, reproducible and potentially scalable manner in the low temperature melting method. CoQ 10 solubility and dissolution increased with increasing concentrations of P 407 in SDs. Comparison of the enhanced dissolution of CoQ 10 from different poloxamers suggested that the preparation of CoQ 10 SDs using P 407 as a meltable hydrophilic polymer carrier could be a promising approach to improve its dissolution.